Anode construction for discharge tubes having rotary anodes



Feb. 23, 1937. 5, BY JONAS 2,071,696

-ANODE CONSTRUCTION FOR DISCHARGE TUBES HAVING ROTARY ANODES Filed Feb. 19, 1954 Patented Feb. 23, 1937 ANODE CONSTRUCTION FOR DISCHARGE TUBES HAVING ROTARY ANODES Gottfried Bruno J onas,- Eindhoven,

. assignor .to C. H. F. Miiller Aktiengesellschaft,

Hamburg, Germany Application February 19,

In Germany March 16,1933 1 Claims. (01. 250-35) present invention relates to anode con-' structions for discharge tubes having rotary' anodes, and more particularly to X-ray tubes having such anodes.

My invention is a continuation in part of my copending application Ser. No. 497,860, filed November 24, 1930, now U. S. Patent No. 1,984,- 583; 1

To dissipate the heat caused by electron bom- "ba1'dment at the anode, the'anode is usually made of a metal of high" heat conductivity, for instance of copper. However, as copper-on account of its low melting point-is not well suited to form the target surface of the anode-i. e. the nizsurface upo -which the electrons impinge-an insertof a metal of higher melting point, as a rule tungsten, is used as the target.

It-ha's been found that the target-surface of .an X-ray tube after it has been in operation for 5, some time, becomes more or less damaged, shows gradually fissures, and finally scales off, which impairs theusefulness of the tube.

Inmy Patent #.1,927,456 and my above referred to Patent #1,984,583, I have described anode congsstructions in which by subdividing the target surface by seams orotherwise, and suitably embedding'it inthe adjoining copper surface of the anode, damaging of the target surface is avoided. According to one feature of myipresent ingy' vention the target surface consists of a thin insert'or cap member of tungsten or similar refractory material, which is in intimate contact'with the copper of the anode, the target surface being provided with radial laminations. In casethe'target is conical, which is usually the case insuch anodes, the lamination is along eneratrices of this cone.

According to a further feature of my invention the target is sub-divided by radially extending grooves converging towards the apex of the cone, the target assuming the shape of a spur gear or conical wheel. Such a construction has the advantage of increasing the area which is subjected to electron bombardment, without reducing the sharpness of the focus.

In such an arrangement the X-ray beam emitted by the anode forms an acute angle with the length direction of the grooves. The grooves are preferably narrow, for instance, having an average width of 0.2 to 2 mm. so that the focus overlaps 1 to grooves.

In order that the invention may be more readily understood and carried into effect, it will be explained more fully with reference to the accompanying drawing, in which:

PATENT amt-E Netherlands,

1934, Serial No. 712,027

Figure 1 is a-schematic bottom view of the target of an anode made according to my invention. I I

Fig. 2 is a similar for the purpose of illustrating of the construction of Fig. 1. 1 I

Fig. 3 is a schematic side view of an X-ray tube having an anode according to my invention.

Fig. 4 is a partly sectionized perspective view of a portion of an anode made in accordance with the invention. I v I I Referring to Fig.-. 3,- the- X-ray tube represents an X-ray tube having a rotary anode, of the general type described vin-the U. S. patent to A; Bouwers No. l,893,'7 59, and comprises an envelope having tubular glass portions l and I, an intermediate metal sleeve 2, which preferably consists of chrome iron, said sleeve being sealed to theends of the glass portions land I'.

The metal sleeve 2 is provided with a rayemitting window I2 through which the active X-rays can emerge from the tube.

The anode or anti-cathode 2|, which will be discussed more fully later on, consists of a tubular copper member-22 having a conical end carrying a conical tungsten target 23, the apex of which is preferably cut off, as shown at 20.

The anode-member 22 surrounds a cylinder 1 of ferro-magnetic material, for instance of iron. The anode is rotatably supported on a stem 5 sealed to the re-entrant portion of the glass cylinder I, suitable bearings 6 being interposed between the stem 5 and the anode-proper.

Opposite to the anode is disposed an incandescible cathode 4 surrounded by a slotted focusing device I3, which is sealed to the re-entrant portion of the glass cylinder I'. v

The anode constitutes the rotor of an inductlon motor the stator of which consists of a magnet system 9 and of a stator winding I I, and is surrounded by a housing III, which is secured to the metallic portion 2 of the envelope.

When the motor is connected to a suitable electrical supply source the anti-cathode is rotated. Such arrangement as is well known permits a very high loading of the tube.

Referring to the anode construction, the tungsten target 23 consists of a comparatively thin tungsten insert or cap member, which may be formed, for instance, by pleating or stamping a tungsten sheet in the form of a grooved conical disc having the shape of a spur-gear and securing the target to a similarly conical end face of the copper anode. Or the copper may be cast on the rear side of the tungsten disc. 55

view of a modification, shown certain advantages As shown in Fig. 4, the target is formed of a thin sheet 24 of refractory material, for instance tungsten, which is provided by pleating or corrugating with radially-extending serrations 25. The serrated sheet 24 is secured to a backing member 26 of good heat-conducting material, for instance cast copper, which member is pro.- vided with grooves corresponding to the serrations 25. at 21 to more clearly show the construction.

While the rear surface of the tungsten target and the corresponding surface of the copper may be smooth, I prefer to make them grooved, as above stated. In any case a very intimate contact between the tungsten and the copper is to be provided.

As will appear, by grooving the active surface of the target, thus the surface upon which the electrons impinge this surface is further increased; this, however, does not reduce the sharpness of the focal spot. As appears from'the drawing, the X-ray beam forms an acute angle with the length direction of the grooves.

Preferably one to ten grooves are provided per fissures and scaling 01f.

Such target construction has also the advantage of very easy and cheap manufacture, as the tungsten target can be conveniently stamped or pleated from a thin tungsten sheet.

It would first seem that the grooving of the target would give rise to considerable temperature differences between its different portions. Such would happen if such grooves were applied I have also found that a parallel grooving as shown in Fig. 2 the shape of the focus continuously changes during operation, a target surface is not symmetrical with respect to the cathode. This drawback is evidently absent with an arrangement as shown in Figs. 1 and 3. 7

While I have described my invention in connection with specific examples and in a specific application, I do not Wish to be limited to same, but desire the appended claims to be construed as broadly as permissible in view of the prior art.

What I claim is:

1. In an X-ray tube of the rotary anode type,

The sheet 24 has been broken away an anode comprising a cylindrical anode body of copper, and a target consisting of a radially pleated thin tungsten sheet, said copper body having a grooved end face conforming to the rear face of said target, said target being secured tact therewith.

2; In an X-ray tube of the rotary anode type,

an anode comprising a cylindrical body of a metal of good heat conductivity and having a substantially conical end-face grooved along generatrices of the cone, a conical cap-member of thin highlyrefractory material of uniform thickness, said cap member covering said end face and being provided with grooves engaging the grooves of said end-face, the average width of the grooves being between .2 and 2 mm.

3. In an X-ray tube of the rotary anode type, an anode comprising a body of a metal of good heat conductivity, a conical end-member of highly refractory material provided on the inner end of said body, said conical end-member being provided over its entire active surface with grooves extending along its generatrices and the grooves being of such average width that the focal spot overlaps a plurality of grooves.

4. In an X-ray tube of the rotary anode type, an anode comprising a cylindrical body of a good heat-conducting metal, said body having a substantially conical end-face grooved in the direction of its generatrices, and a corrugated conical cap-member of thin refractory material, the corrugations of said cap-member fitting into the grooves of said end-face.

5. An X-ray tube comprising an evacuated envelope, an anode structure, and a cathode strucextending along the generatrices of the surface. 6. An X-ray tube comprising an evacuated envelope, a rotatable anode, and an electron-emitting .incandescible cathode, said anode opposing said cathode with a conically-shaped surface, said surface being provided with contiguous grooves extending along the elements thereof.

7. An X-ray tube comprising an evacuated envelope, an anode structure, and a cathode structure, said anode structure comprising a rotatable and extending in a direction from the axis of rotation to the periphery, said grooves having an average width between .2 and 2 millimeters.

GO'ITFRIED BRUNO JONAS. 

